NEW BEDFORD - A Catholic church that has been a glittering and vibrant part of the Portuguese community here for a little more than 140 years will be closing its doors and merging with another neighborhood parish, the Diocese of Fall River has announced.

In a statement released Monday and posted on its website, the diocese said St. John the Baptist Parish, which was established in 1871 and calls itself the first Catholic church serving the Portuguese community in North America, will close and merge with Our Lady of Mount Carmel Parish, though a date for the merger has not been set. The diocese cited mounting debt and declining membership for the decision.

“Parishioners, of course, were extremely sad’’ when a letter announcing the closing was read during Masses over the weekend at St. John’s, the Rev. John J. Oliveira, the pastor of both parishes, said in a phone interview Tuesday.

He said that St. John’s is carrying about $205,000 in debt and that it is unclear what will happen to the property when the church closes.

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Oliveira said that while Our Lady of Mount Carmel, which is less than a mile from St. John’s, also serves the Portuguese-American community, St. John’s parishioners are free to join whatever parish they choose.

“I’m very confident that these folks who are committed to their faith will continue to live it vibrantly’’ wherever they go, he said.

Joe De Frias, 72, lives across the street from St. John’s and said he has been a parishioner for 46 years. He said his three children and five of his grandchildren were baptized there.

The church celebrates Mass in Portuguese every Sunday at 8 a.m. and 11 a.m., according to the diocesan website.

De Frias said he and his wife, Maria, have always tried to help the church by making donations and volunteering on feast days, setting up tables and cooking dishes for the revelers.

“Well, I can’t do anything’’ about the closure, De Frias said.

He said he and his wife will probably start attending Our Lady of Guadalupe at St. James Church, several blocks from St. John’s.

The diocese said in the statement that while St. John’s had added 52 households since October 2009, attendance at Masses in that period fell from an average of 565 parishioners per weekend to 488 in November.

The diocese said the membership numbers represent a significant decline, though it did not provide totals from previous eras. Oliveira, who has been the pastor for about two years, said he did not know what the totals were at the height of the parish’s popularity in earlier decades.

‘I go every Sunday, 11 o’clock. That’s my house for 40 years.’

Joe De Frias , Parishioner of 46 years who lives across the street from St. John’s

Also, the diocese said, a goal was set in October 2009 to raise $750,000 for repairs to the church, but just $129,000 had come in by the middle of last year, and parishioner participation in the capital campaign was at 17 percent.

The statement said all the money raised in the capital campaign will be returned to donors.

The original church was destroyed by a fire in 1908, and the current building was dedicated in 1913, the statement said. Repairs have been put off because of the debt, with the exception of recent emergency repairs to the roof, the diocese said, resulting in interior water damage with each successive storm.

In the letter read to parishioners announcing the closing, Bishop George W. Coleman, who leads the diocese, wrote that the change may be difficult for some.

“We grow attached to communities and churches,’’ Coleman wrote. “When changes such as these arrive, based upon demographics and economics which are beyond our control, it becomes difficult to accept.

“Our commitment to the church’s mission of evangelization, however, remains unchanged amidst all that is changing around us.’’

Danisa Da Silveira, 23, lives near St. John’s and was surprised when a reporter told her it was closing. She recalled the outdoor festivals the church used to have that drew the entire neighborhood when she was a child.

“They used to shut down the street and light everything up,’’ she said. “It was huge.’’

Da Silveira said the festivals often included live music and Portuguese cuisine.

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